Assionobs to commercial solvents cobpobation



- Patented Sept. 6, '1932 UNITED s'r rEs PATENT ounce (LEO M. CHRISTENSEN 'AND I; 'IOGU'IOEAI, OI ram KAO'TI, mums,

. ASSIGNOBS TO QOHIERGIAI: SOLVENTS A CORPORATION OF MARYLAND CORPORATION, OF DEBBIE EAUTI, INDIANA,

PROCESS OF PRODUCING ACIDS BY IEBIDITA'IION OI Io Drawing.

This invention relates to the production of such materials as acetic and butyric acids,

' ethyl alcohol methane, hydrogen, carbon d1- oxide and other useful products b the fermentation of cellulosic materials. ore particularly, it relates to the fermentation in such a process, of cellulosic material remain- I ing after the treatment of corncobs and other has described methods of fermenting celluconsuming animals, and accordingly a conlosic material by the aid of thermophilic bacteria which produce acetic and butyric acids, ethyl alcohol, and gases such as carbon dioxide, methane, and hydrogen. According to the. method described in these patents, a mash is prepared from some comminuted form of cellulosic material such as, for example, corncobs. This mash is then inoculated with a mixture of organisms capable of. producing acetic and butyric acids and of the character ordinarily found in almost any form of fermenting vegetable matter, stable manure, pond mud, septic sewage, tank mud, soil, etc. These organisms are usually found in the intestinal tracts of cellulosevenient form 'of inoculum is obtained by selecting material from the center of a steam ing stable manure heap or from such other source as is ;most convenient or suitable. Since these organisms are also usually foundon corncobs, it is possible, if desired, to'make use of the thermophilic bacteria naturally occurring in the corncobs as the'means of inoculating the mash. After inoculation, fermentation is allowed to take place at temperatures ranging from to 70 C., but preferably at temperatures in the neighborhood of C. v

Like all protoplasmic bodies, bacteria consist of carbon oxygen, hydrogen, and nitrogen, together with inorganic salts and vary* 1 ing quantities of phosphorus and sulfur. In

order that bacteria may develop and multiply, therefore, they must be supplied with these substances in proper quantities and in suitable form for assimilation. The first Application filed mic 14,1000. sci-m Io. use;

theree. materials named are present in the cellulose used as the raw material. Certain of the other required materials are usually present in small but insuflicient quantities with the raw material used as the source of the cellulosic material. These necessary nutricuts are usually supplied in the form of varying pro rtions 0 such materials as potasslum 5153mm, sodium phos hate, ammonium chloride, ammonium s phate, potassium chloride, distillery wastes such as slops from the butyl-acetonic fermentation ess, steep water, etc. 7

It has been found that, in general, bacteria which produce acids during the course of a fermentation become-less and less active as procthe concentration of acid in the medium increases. After a certain point is reached, the action of .the bacteria becomes neglible unless the acid is removed from the medium. Such a condition is met with in the present case. Langwell, in the patents cited above, has recommended that the hydrogen ion concentration of the fermenting medium be maintained within the limits of. about pH 5.0-pH 9.0 measured in the bulk .of the mash by the employment of a) oxides hydroxides, carbonates or bicaismnates of alkali metals, including ammoniumifor (b) oxides, h droxides, carbonates, or carbonates of a aline earth metals, including mag nesium, in which cases compounds of alkali metals which cause the formation of insoluble alkaline earth metal compounds are added from time to time. It is preferred to follow the procedure outlined under (a) in which case it is necessary to make small additions of the neutralizin agent at intervals throughout the course 0 the fermentation. Whatever method is resorted to, the mash should be agitated at frequent intervals or acetic and butyric acids and other useful products by the fermentation of cellulosic materials with thermophilic bacteria, various forms of naturally occurring cellulosic material as well as waste materials from other processes have been investigated. In many cases it has formerly hot been found ossible to ferment this latter type of material with satisfactory ields for various reasons. A material of is character is that sometimes desi ated as xylose residue.

T exact chemical structure of neither cel lulose nor cellulose-containing materials is known. It is fairly well established, however, that in different forms of ve etation the cellulose occurs in somewhat 'fierent structural forms, for example, 0:, J3, and y cellulose, lignocellulose, pectocellulose, hemicellulose, etc. Attempts have been made to utilize these diiferent forms of cellulose in many different ways. Much attention has been devoted to hydrolyzing various forms of cellulosic material to pentoses such as xylose. This is accomplished, for example, by treating cellulosic materials such as corncobs, corn stalks, sawdust, straw, etc. with a dilute acid such as sulphuric acid, either at ordinary or'at elevated temperatures. From corncobs yields of xylose as high as 30-35% may be obtained under favorable conditions, the xylose being formed from the more reactive portions of the cellulose. The more resistant forms of thecellulose may, if desired, be converted to cellobiose, glucose, or polymers of glucose by treatment with concentrated acld. Treating fresh cellulosic material with concentrated acid, however, appears to destroy that ortion of this mate'- rial giving xylose, an little or none of the latter material is obtained. Hence it results that in manufacturing pentoses .such as xylose, appreciable amounts of cellulosic materialsare left in the solid material remaining at the end of the operation. At the same A time, however, the proportions of other unhydrol zable materials are materially increase In the commercial production of xylose, for example, by treatin corncob meal with hot dilute sulfuric acid, t e amount of lignin in the residue amounts toabout 48% as compared to about 35% in the untreated material.

Many attempts have been made to ferment this cellulose-containing residue from the manufacture of xylose, as disclosed above for the production of acetic acid and butyric acids and other useful products by fermentation with thermophilic bacteriai I For some unknown reason, however, the yields based "on the amount of cellulose known to be present. were uniformly appreciably lower than the results obtained from cellulosic material, which had not previously been subjected to the hydrolyzing treatment.

It has now been discovered that the former. disadvantages inherent in the use of xylose Lenses residue as a raw material for use in cellulosic fermentation processes may be satisfactorily overcome by employing a modified procedure which consists essentially of regulating the hydro en ion concentration of the fermenting me ium alternately with ammonia or ammonium compounds and thenv with alkaline materials such as the oxides, hydroxides, carbonates or 'bicarbonates of alkali metals or alkaline earth metals. Such a procedure results in the production of higher yields of volatile acids than by hitherto used methods. Higher yields are also obtained than when using either of these neutralizing agents alone, The reason for the improved results obtained in this manner is not known, but it-appears as if, in addition to the neutralizing action, the ammonium ion under the articular conditions emloyed, has a stimulating action. upon the acteria or elseimmunizes them for a time a ain'st some toxic agency in the raw material being fermented. Or, it maybe that the improved results are due to a combination of these factors.

The process may be satisfactorily oper atedin a number of ways depending upon the method of conducting the fermentation the method of recovering the products 0 certain cases, however, where it is required to 105 recover by a particular method as much as possible of the neutralizing agent the procedures just described are not satisfactory and require certain modifications. In a co pending application, U. S. SeriaLNo. 407,295,

filed November 14, 1929, has been disclosed a continuous method of fermenting cellulosic materials. According to this process,

at the conclusion of the fermentation, the J greater portion-of the fermented mash is removed from the fermentation vessel, ap-

proximately 10% being left behind to serve as the inoculum for a subsequent fermentation. When carryingo'ut the fermentation 12o in this manner, ammonia may be used as the neutralizing agent throughout one fermentation and soda ash throughoutlthe succeed-' ing fermentation. subjecting the bacteria,-

fermentation, to the action of ammonia or an, animomum compound through onefermentation cycle lastin for several days and then to the. actionof t e alkali or alkaline earth neutralizing agent through a similar 811cuh which are used as the inoculum for the new the desired improved results.

In carrying out the present improved'process, a mash is made up from comminuted xylose residue in suflicient quantity to give, say 67% concentration by weight, altho other concentrations may also be employed. The mash may be made up with water, in which case it is customary to add nutrients in the form of such materials as potassium sulphate, potassium chloride, sodium phosphate, ammonium chloride, etc. In case distillery wastes, such as butyl acetonic fermentation slops, are employed as the source of the nutrients the mash may be made up wholly or in part from the distillery slop instead of water, depending principally upon the concentration of the distillery waste. The hydrogen ion concentration of the mash is then regulated so as to be within the limits pH 9 and pH 5, and preferably at pH 7.3

measured Within the bulk of the mash with Sod either (a) ammonia, ammonium carbonate, or ammonium bicarbonate, or (b) soda ash or other alkali metal or alkaline earth metal, oxide, hydroxide, carbonate or bicarbonate. After inoculating with thermophilic bacteria capable of fermenting cellulosic material and producing such materials as acetic and butyric .acids and other useful products, fermentation is allowed to take place at temperatures ranging from to C.- and preferably at about 60 C. During the fermentation. the hydrogen ion concentration of the fermenting mash is maintained within the abovementioned limits by further additions of either the neutralizing agents designated under (a) or (b) or of mixtures of. compounds selected from each group. In

' .case the neutralization during the entire fermentation period is effected by the aid of agents selected from only one of these groups,

inoculum for a subsequent fermentation is taken from this fermenting mash and a neutralizing agent selected from the alternate group used during the succeeding fermen-- tation period. In this way a fermentation cycle is obtained whereb the same bacteria are carried through a series of fermentations alternately neutralized with compounds of groups (a) and Instead of alternating the neutralizing agent during a particular fermentation or even during succeeding fermentation cycles, the neutralizing a ent may only be changed as often as needed to give the desired results. At the conclusion of the fermentation the products formed may be recovered in a number of ways, the particular one chosen depending upon a number of factors which need not be considered at this point.

In the table following are shown average; results from a series of experiments carried out as hereinabove disclosed. In each case the mash was made up from wet xylose residue and distillery slop from the butyl acetonic fermentation industr Ineach case 10% of mash from a prece 'ng fermentation was used as the inoculum. The fer? mentations were carried out at a temperature of 60 C. and the hydrogen ion concentration was regulated to approximately pH 7 .3 by the addition twice each day of the indicated neutralizing agent. The ammonia used in these fermentations was either the anhydrous or the 26% aqua grades. There are a number of 'fermentations of each kind included in these average results.

Table Neutralizing ag Xvloseresidue Volatile acid ratio acetic per y cent of For fermentation For preceding fermentation Soda ash Ammonia. Ammonia--. Soda ash Soda ash Ammonia-.. Ammonia.

Ammonia. a ash... Soda ash Soda ash Soda ash.-- Ammonia Ammonia.

The results shown above indicate a very distinct improvement in yields when using the alternate neutralization process set forth herein.' Using ammonia as the only neutralizing a ent will generally give somewhat better yields than when using soda ash alone as the neutralizing agent. The improvedresults shown by the use of the former are gradually lost after a period of time but by subjecting the bacteria to the alternate action of the'two types of neutralizing a ents either during a single fermentation cyc e or in alternate fermentations over a series of cycles gives distinctly higher. yields thanby the use of either type of neutralizing agent alone; In 'anyprocess such'as the presentwhere the cost of the raw material being fermented represents such a largepercentage of the total cost of operating the process, even slight increases in yields are highly important.

Now having described our invention, what we desire to claim as new and novel is:

1. In a process for the. fermentation of cellulosic material with thermophilic bacteria, the step which comprises maintaining the hydrogen ion concentration of the ferment ing medium within the desired limits during the fermentation cycle by the alternate use of ammonia and soda ash.

2. In a process for the fermentation of xylose residue with thermophilic bacteria,-

the step which comprises maintaining the xylose residue with thermophilic bacteria, the lso tion.

step which comprises maintaining the hydrogen ion concentration of the fermenting medium within the desired limits during the fermentation cycle by the use of ammonia and soda ash.

4. In a process for the fermentation of cellulosic materials by means of thermophilic bacteria, the steps which comprise neutralizing the fermentlng medium with a neutraliz-- ingagent selected froin'one of the groups consisting of (a) ammonia, ammonium carbonate and ammonium bicarbonate, and (b) oxides, hydroxides, carbonates and bicarbonates of alkali metals and alkaline earth metals, allowing the fermentation to proceed and subsequently neutralizing the fermenting medium'with .a neutralizing agent selected from the group not used in the previous neutraliza- 5. In a process for the fermentation of xylose residue by means of thermophilic bacteria, the steps which comprise neutralizing the fermenting medium with a neutralizing agent selected from one of the groups consisting of (a) ammonia, ammoniumcarbonate and ammonium bicarbonate, and (b) oxides, hydroxides, carbonates and bicarbonates of alkali metals and alkaline earth metals, allowing the fermentation to proceed and subsequently neutralizing the fermenting medium with a neutralizing agent. selected from the group not used in the previous neutralization.

6. In a process for the fermentation of cellulosic materials, the step which comprises effecting the fermentation with thermophilic bacteria which were utilized in a previous fermentation, said previous fermentation having been neutralized with a neutralizing agent selected from one of the groups consisting of (a) ammonia, ammonium carbonate and ammonium bicarbonate, and (b) oxides, hydroxides, carbonates and bicarbonates of alkali metals and alkaline earth metals, and maintaining the hydrogen ion concentra tion within the bulk of the fermenting mash within the desired limits by means of a neufectin tralizing agent selected from the group not used in the previous fermentation.

7. In a process for the fermentation, of xylose residue, ,the step which comprises ef the fermentation with thermophilic bacteria which were utilized in a previous fermentation, said previous fermentation having been neutralized with a neutralizing agent selectedifrom one of the groups consisting of (a) ammonia, ammonium carbonate and ammonium bicarbpnate, and (b) oxides, hydrorrides, carbonates and bicarbonates of alkali metals and alkaline earth metals, and maintaining the hydrogen ion cencentration within the bulk of the fermenting mash within the desired limits by means of a neutralizing agent selected from the group not used in the previous fermentation.

8. In a process for thefermentation of cellulosic materials, the step which comprises effecting the fermentation with thermophilic bacteria which were utilized in a previous fermentation, said previous. fermentation having been neutralized with ammonia, and maintaining the hydrogen ion concentration within the bulk of the fermenting mash within the desired limits by means of soda ash.

9. In a process for the fermentation of xylose residue, the step which comprises effecting the fermentation with thermophilic bacterla which were utilized in a previous fermentation, said previous fermentation having been neutralized with ammonia, and maintaining the hydrogen ion concentration within the bulk of the fermenting mash within the desired limits by means of soda ash.

, 10. In aprocess for the fermentation, of cellulosic materials, the step which comprises effecting the fermentation with thermophilic bacteria which were utilized in a previous fermentation, said previous fermentation having been neutralized with soda ash, and

maintaining the hydrogen ion concentration within the bulk of the fermenting mash within the desired limits by means ofammonia.

11. In a process for the fermentation of xylose residue, the ste which comprises effectin the fermentation with thermophilic bacteria which were utilized in a previous fermentation, said previous fermentation having been neutralized with soda ash, and maintaining the hydrogen ion concentration within the bulk of the fermenting mash within the desired limits means of ammonia.

In testimony whereof we afiix our signatures.

LEO M. CHRISTENSEN. WINFRED N. MGCUTCHAN. 

